We restrict for some lines the study to the stationary case.
The reader can check straightforward that our previous computations remain almost unchanged for the elliptic setting.
We now can apply the result of Lemma 4.4. page 61 in [1]} mentioned above.
It allows to infer from (REF ) with \(m=2\)  that
\(\int _{K_\rho } \vert v_i \vert ^2 \vert \nabla u_i \vert ^2 \le C(N,C_s,s,\Vert Q \Vert _{L^{s/(s-1)}(K_{2\rho } )}) \rho ^{(s-N)/2s}\int _{K_\rho } \vert \nabla v_i \vert ^2 .\) 
